Should materials stay or go?

Most building materials eventually wear out. But before they fail completely, you have two choices: cover them or remove them when you install replacements. Burying problems is tempting because it saves the hassles and costs of demolition and disposal. But those savings can evaporate when buried problems fester and disrupt the new materials above them.

Here is a look at six common surfaces -- inside and outside -- and guidelines about burying them or tearing them down and starting from scratch.

Wallcoverings. A wall with many surface problems is a good candidate for a cover-up because stripping old paper can be is time consuming and messy.

Some heavy vinyls can be stripped cleanly from drywall, particularly if the wall was primed with paint. If not, wallpaper adhesive sets in the surface of the drywall, and when you strip the wallcovering you strip a lot of the drywall surface as well. That can leave the drywall scarred beyond repair.

Drywall. Gypsum drywall damaged beyond the point of spackling can be resurfaced with thin panels only 1/4 or 3/8-inch thick, or with wood paneling.

Thin panels work because they have the old drywall for support between studs.

The drawback is that even thin sheets alter the wall thickness. Otherwise, new drywall or paneling simply butts against the molding around windows and doors.

Ceramic tiles. Problem tile floors should be removed, particularly in wet areas where eroding grout allows water to seep into the floor and break the adhesive bond. Eventually, it can delaminate and rot the plywood underneath.

If the floor seems spongy, tile has to come up so the subfloor can be checked.

If it's rotting, some of the plywood will have to come up to get a look at the floor joists that support it.

Soffits. The underbelly of the roof overhang is a common source of trouble. If the plywood is wavy and spongy, it has to go. Otherwise, new materials won't lie flat. If old plywood is solid and you want to end periodic scraping and repainting by adding maintenance-free vinyl or aluminum, leave the old soffit in place. But be sure that air flowing through a new, perforated soffit system won't be blocked by the old plywood.

Roof shingles. Reroofing is the job that most often raises the bury-or-remove question. And there can be a lot riding on the answer. If old shingles need to be removed, a contractor will have to rent a roll-off container, arrange for disposal, and spend extra time stripping the roof. If the old shingles stay, the job will be much faster and less expensive. The decision to bury or remove depends on two things: the condition of the existing roof surface and the number of roofing layers already in place. If only a few tabs (the exposed sections) are damaged or missing, you generally can patch them and reroof over the existing layer. But if many tabs are brittle and curling, a new layer of shingles won't lie flat and may leak. If you're reroofing due to leaks, a contractor needs to peel back some shingles and tar paper to check the plywood roof deck. When water has seeped through the layers of protection, you may need wood repairs in addition to shingle repairs.

Siding. Whether you bury or remove old siding also depends on the condition of the material, but also on what you want to accomplish with the project. Most old siding can be renailed or screwed down as needed to provide support for a new layer. The drawback in leaving it is the extra thickness. Even a slim profile of new vinyl siding can bury the exposed edges, called reveals, around window and door trim. If you apply new clapboards or siding panels, their extra thickness becomes even more of a problem. You would have to pay a contractor to pull all the exterior trim, increase the depth of all window and door casings, and then reinstall the old trim. Stripping old siding allows you to stay with the existing trim, and to make improvements to the exterior walls, all without disrupting the interior surfaces.